From mboxrd@z Thu Jan  1 00:00:00 1970
From: Eli Zaretskii <eliz@delorie.com>
To: gdb@sources.redhat.com
Subject: i386 register numbering
Date: Sat, 28 Jul 2001 03:14:00 -0000
Message-id: <200107281012.GAA02314@delorie.com>
X-SW-Source: 2001-07/msg00392.html

Consider the following program:

#include <stdio.h>

double one = 1.0;

int main (void)
{
  double d;

  d = 2.0*one;
  printf ("%f\n", d);
  return 0;
}

Now observe:

  gcc -g -O -o ftest.exe ftest.c
  gdb ftest.exe
  (gdb) break 10
  Breakpoint 1 at 0x15fe: file ftest.c, line 10
  (gdb) run
  Starting program: ftest.exe

  Breakpoint 1, main () at ftest.c:10
  10	printf ("%f\n", d);
  (gdb) info address d
  Symbol "d" is a variable in register ds.

In fact, `d' is in st(0), of course.

This happens because the numbering of registers used by GCC differs
from the one used by GDB, see gcc/config/i386/i386.h in the GCC
distribution.  Since i386.h seems to be common for all i386 targets,
I'd expect this problem to pop up on other x86 targets as well (the
above was tested with DJGPP native debugging).

Do others indeed see this bug?  If so, what would be the best way of
fixing it?